post https://app2test.infiniaweb.com/infinia_api/v1/payments/refund/
Create a refund for a payin. Only completed payins are eligible for refunds.
A refund may still fail after being initially marked as SUCCESS; in such cases, you'll receive a callback with status = FAILED.
To simulate a failed refund in the sandbox, create a payin with amount = 101 (see the Create Payment endpoint for details).
To refund a deposit, use the Create Refund endpoint from Accounts.